Sunday, March 11, 2007

Detecting Change

One of the topics I talk about in my Archaeological Method and Theory classes (ANTH 455/555 and 456/556) is the challenge of taking a time-like (materialist) view of the world over a space-like (essentialist) view. Although conceptually we can imagine (or at least pretend to imagine) conceiving of the world where change is continuous and "things" are really events at different temporal scales, our common sense tells us otherwise. Thus, what we see as a "table" is a snapshot (i.e., a particular combination of attributes - or more generally, an event) of a continuously changing set of attributes. Imagine having a time-lapse camera in your head where you can watch an object in "fast forward" mode from the point of its creation to some far distant point. When we do that, the idea of "table" becomes fairly arbitrary because we can view the table from trees to lumber to table to table with marks on it, to wobbly table to refinished table to broken table to firewood to fire (or whatever unique history occurs). The idea of "table" only has meaning as a thing at specific instances in time. This is taking a "time-like" view of the world - and its vital to constructing a scientific understanding of history. Of course, humans are not particularly well-suited to conceiving of the world this way. Our "default" position is that things are real and unchanging. Yeah, we can understand that things change but we are not really good at detecting change. We are good at seeing difference but change is an effect that we largely understand in terms of difference. This has a number of consequences. First, as my colleague Mark Madsen pointed out to me, the cognitive mechanisms that filter information coming from the eyes highlight the irrelevance of the "realism" and "non-realism" debates in the philosophy of science. While there is some "world" out there, we can never escape the set of filters by which we observe it. In addition to all of the culturally mediated (in the Hanson 1958 and Osgood 1951 sense), we can never perceive "reality" since we don't have the mental machinery to do it. The second consequence is that our fallback position (i.e., common sense) is one of essentialism (space like views). If we don't specifically try to build explicit measurement systems (i.e., classification) we will end up making assumptions about thing-ness that embodies space-like perceptions. In other words, we will treat our observations in the here-and-now as if they are the "real" world. The degree to which this aspect of our perception and observation systems is limited by our mental machinery has been demonstrated through a series of experiments by cognitive psychologists. One of the coolest I've seen is a series of videos that demonstrate how poor we are at sensing change. These were done at the Visual Cognition Lab at the University of Illinois. You can read more about the Visual Cognition Lab and see more examples at:

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